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By John M. McAnerney

In 1955, the U.S. Army started to experiment in Greenland with tunneling in glacial ice and later in frozen glacial moraine. By 1960, long adits and experimental rooms had been successfully excavated. Full mechanization with coal-cutting machinery was most efficient in ice but drilling and blasting were necessary in bouldery moraine. In 1963, the U.S. Army Cold Regions Research and Engineering Laboratory, (USA CRREL; redesignated U.S. Army Terrestrial Sciences Center July 1, 1968) started a tunnel in the frozen silt of central Alaska near Fairbanks. The original adit of 360 ft (109 m) was successfully driven in the permafrost by a twin-rotor tunnel-boring machine, the Alkirk Cycle Miner. The workings were enlarged in 1966 and 1967 by standard mining techniques in which jackhammers, steam points, and augers were compared. A mechanical coal cutter was tried to supplement drilling and blasting. In 1968, airblasting techniques were used successfully for breaking out the frozen silt. All mine products were loaded mechanically and hauled by self-dumping shuttle car. Pneumatic methods of transport were tried for both dust removal and for conveying blast products up to 3-in. maximum size. Studies of the effects of natural winter ventilation through a shaft showed that tunnel closure could be reduced by lowering the adjacent ground temperature. It is concluded that underground openings in frozen ground should be cut and maintained at well below freezing temperatures to hold deformation to a minimum. HISTORICAL BACKGROUND This chapter deals with aspects of tunneling not previously discussed in the conference papers in this book. The chief differences are that the three tunnels lie entirely within frozen material and are relatively small, since they were constructed mainly for research. The primary objectives of the research were to develop underground shelters for military per-

Jan 1, 1970

By Martin Epner, Eric Gregory

DURING the past decade, considerable work has been carried out on various cermet systems in an effort to produce materials suitable for high-temperature applications in gas turbines. Most of the materials have not, as yet, met the requirements of the engine manufacturers, primarily because of their lack of room-temperature ductility and thermal shock resistance. In the field of tool materials, however, although ductility is still of prime importance, much has been accomplished by improving design parameters and the quality of carbide materials with a view to using cermet compositions successfully. The systems described in this paper were designed primarily for application in this field, although their development was a natural outcome of work on similar compositions designed for high-temperature service. In steel-bonded titanium carbide, the steel binder imparts heat treatability to the system while the carbide provides abrasion and wear resistance. Combining the carbide and the steel matrix in carefully controlled proportions results in a composite material which, when the steel is hardened, has man of the properties of cemented tungsten carbide. In the annealed condition, this material can be readily machined by the conventional chip-removal techniques. Titanium carbide has certain distinct advantages over many of the other carbides when combined with a steel matrix. It is among the hardest of the carbides and is one of the most stable. Liquid iron wets titanium carbide, and this wetting assists in the formation of a dense cermet. Once the composite structure has been formed, the titanium carbide acts as a relatively inert phase during the heat treatment of the matrix. PREPARATION OF ALLOYS The steel-bonded titanium-carbide materials described in this paper were prepared by the liquid-phase sintering technique. The titanium carbide used had an average particle size of 6 to 7 p, a total carbon content of 19.4 pct and 0.35 pct free carbon. This was blended with the elemental metal powders by ball milling them together in a hexane medium. After drying, paraffin wax was added to the blend to provide green strength in the pressed briquettes, and compacting was performed at 15 tsi. Liquid-phase sintering was carried out in vacuum at temperatures which depended on the chemical composition of the system involved, but which were usually around 2640° F. The resultant materials had a density approaching 100 pct of theoretical. The

Jan 1, 1961

By Eugene A. Stephenson

In most instances the fluids produced from underground reservoirs have been described as they appear at the surface, and usually it has not been necessary to distinguish between surface and reservoir phases. More recently it has become imperative to recognize the fact that changes in phase may occur between the reservoir and the receiving unit. The simple terminology of "wet" and "dry" gases and "crude petroleum oil" served our needs fairly well in the shallow, low-temperature and low-pressure fields. It has been left to the legislatures, regulatory commissions, and courts to decide whether a field is or was a gas field, an oil field, or both. This they have done by direct definition and also by implication. For example, in Texas:' (d) The term "gas well" is any well (a) which produces natural gas not associated or blended with crude petroleum oil at the time of production, or (b) which produces more than one hundred thousand (100,000) cubic feet of natural gas to each barrel of crude petroleum oil from the same producing horizon, or (c) which produces natural gas from a formation or producing horizon productive of gas only encountered in a well bore through which crude petroleum oil is also produced through the inside of another string of casing. (e) The term "oil well" is any well which produces one (1) barrel or more of crude petroleum oil to each one hundred thousand (100,000) cubic feet of natural gas. In the state of Louisiana, the same general result is achieved largely by the following paragraph :* Wells producing both oil and gas shall not waste or blow into the air an amount of gas of more value at three cents per thousand cubic feet, than the market value of the oil recovered. The Commissioner of Conservation shall allow a reasonable time to determine the status of any well. This means that for wells making both oil and gas, if n represents the price of oil in dollars, and x the allowable gas waste expressed in M cu. ft. Per day,

Jan 1, 1938

By R Engle, R P. McMahan, D A. Bowman, S Schafrik, W Thabet

Preventing injuries and fatalities related to conveyor system use in the mining industry is important and increases uptime while decreasing lost time. The research presented here is funded by the National Institute for Occupational Safety and Health (NIOSH), and intended to accomplish this prevention by the use virtual environments (VEs) to improve training and help miners better understand the hazards of working around conveyor systems. Two conveyor system VEs designed to teach miners about hazards and to safely complete tasks around conveyor systems were developed for this project. The first conveyor system VE, called the instructional tour, gives the miner a semi-automated tour of a conveyor system and teaches the miner about possible hazards (eg, missing guarding) and how to safely fix conveyor problems (eg, a stuck idler) using lock-out, tag-out procedures. The second, called the virtual shift, allows the miner to freely navigate around a conveyor system to detect and avoid hazards. The miner is presented with equipment failures that need to be safely repaired during the virtual shift. If the miner fails to identify and avoid a hazard or fix a failure in a safe manner, an animation of the consequences is shown to the miner, who must start the virtual shift over. The models for the conveyor system VEs were created using 3DS Max. Desktop versions of the VEs were then created using Deep CreatorÖ, an authoring application for creating interactive 3D environments. Later, more realistic versions of the VEs were created for CAVEÖ, a room-sized visualisation system, using DIVERSE, an application programming interface. In initial evaluations of the conveyor system VEs, mining colleagues have indicated great interest in such training tools. According to their feedback, these and similar VEs would provide excellent alternatives to normal classroom training and serve as positive precursors to hands-on experience. These VEs provide new miners a chance to experience hazards associated with working around conveyor systems without being in possible danger.

Jan 1, 2008

By Charles A. Kumke

The ('slot" system of mining in use at the Golden Queen mine, Mojave, Calif., does not involve any new mining methods. It is, however, a new combination and adaptation of several stoping systems in common practice. The first plans for stoping operations at the Golden Queen mine called for ordinary shrinkage stopes. The hanging wall of the vein, where exposed, is a very hard felsite with a dip varying from 50° to 70°. The vein itself is quartz, shattered and fractured enough to make it easy to drill and blast to a clean hanging wall. There is no well defined footwall. The footwall limits had to be determined by assays as the metal content faded out into the felsite. Two shrinkage stopes, each approximately 200 ft. long, were laid out and started on the 200-ft. level. One of these stopes, varying in width from 8 to 18 ft., was carried on up to the top limits of the ore, approximately 120 ft., without a break in the operation. The shrinkage system proved entirely satisfactory and low costs resulted from this operation. In the final drawing of this stope, two timbermen followed down on the ore, scaling the hanging wall clean of small fragments and placing an occasional long stull from foot to hanging wall where it was deemed necessary. Few such stulls, however, were required. The hanging wall stood up very well until the stope was entirely emptied of ore. Waste fill was then put into the stope by the glory-hole method, through a waste raise that had previously been run to surface from the middle of the stope. The second shrinkage stope ran into difficulties about 35 ft. above the sill floor. Up to this point the maximum width of the ore had been about 15 ft. The ore suddenly widened into the footwall to a distance of 40 ft. in the north end of the stope. In extending the stoping operations over this, width, it was soon found that the vein material would not arch and support itself. Drilling in this end of the stope was then entirely too hazardous, and all operations were stopped. The ore was drawn through the chutes below as rapidly as possible and as soon as the stope was entirely

Jan 1, 1937

By Harry H. Power

WHILE the attention of all engineering branches is focused today on changes and improvements in the several curricula, we are concerned here with the many questions arising in industry and college concerning the preparation for the petroleum engineering profession. The succession of problems confronting the petroleum engineer demands a degree of versatility not ordinarily encountered in other professions. As a consequence, the student cannot acquire mastery of all the several engineering branches represented in field practice, and as an alternative, he has learned to appreciate the value of thorough training in the basic or fundamental sciences as a preliminary foundation for professional work. While our attention is directed primarily to the training of engineers in educational institutions, it is necessary that the ultimate education of the professional engineer be kept in mind. It is apparent that his success as an engineer is limited not only by his educational and job experience, but by his native endowments: mentality, personality and health. The engineer's lack of job experiences often proves as much a handicap as the lack of adequate college training. If the final product proves to be satisfactory, both industry and technical institutions are to be congratulated. However, if the product is found wanting, the one most responsible should be apprehended. FITNESS FOR PROFESSION For the most part, students of engineering colleges have had their interests in applied science awakened at a relatively early age. Many of them entered college as a convenient means of acquiring a technical education, but undoubtedly would have had better prospects in a shorter program offered by institutions of noncollege grade. The activating motive of practical interest is also strong in students suitable for college training, but in many cases an intellectual interest must be awakened in order that it may survive graduation. Numerous engineers believe that this progressive process of selection and determination of career aims is one of the essential services rendered by the engineering colleges. Industrialists, who are more interested in quality than quantity of petroleum engineering graduates, have pointed out the good that should result if more empha¬sis were given to the work of eliminating the misfits. They also point out the protective measures that have been taken by other professions for the betterment of professional standards. Mention has been made of the beneficial results to be obtained by collective determination of the market for the products of engineering schools, particularly in that the students unsuited to the profession would have an opportunity to prepare themselves for employment more suited to their personalities and other qualifications. In the event that such a system of coordinated personnel direction is developed by the

Jan 1, 1941

By C. T. Bischoff

This paper describes the results of testing with colorimetric methods, using "dithizone", soil samples taken over various known copper and zinc deposits covered by glacial till. Variation in results is shown for different depths and types of overburden as well as grade and type of deposit. Limiting factors for the practical application of this work are discussed. The method has proved successful for copper and zinc deposits under clay and fine sand with depths up to at least 30 ft but fails in coarse sand and gravel unless depths are very shallow. Swamps require penetration to the underlying subsoil for sample material. DURING the past few years geochemical testing for traces of heavy metals in water, soil, rock, and vegetation has aroused increasing interest. Various techniques for field and laboratory determinations have been described in the literature, as have some of the results of application. However, little information has been published regarding application to glacial terrain. Over 90 pct of the Canadian Shield is overburdened, resulting in high costs for mineral exploration once the outcropping ore deposits have been found. This has been largely responsible for the widespread application of mining geophysics in Canada, permitting concentration of effort on area or zones considered most favorable. However, geophysical interpretation has its limitations, since at least 90 pct of the structures indicated thereby contain no valuable minerals. A more direct approach is therefore highly desirable. If underlying base metal mineralization can be detected by sampling soil or vegetation at moderate cost this should prove of great help in locating new discoveries or extending known ones. A large proportion of Canadian ore deposits contain appreciable copper or zinc, even where these are not the principal economic metals. Consequently the field of application is a broad one. This paper deals with investigations along these lines with particular emphasis on soil sampling. The problems involved from the start were: 1—Which types of glacial soil, if any, would best lend themselves to testing, and conversely which types might be considered relatively hopeless? 2—Through what depths of overburden could significant mineralization be detected? 3—What sampling techniques would prove economically applicable? This included minimum depth of sample and maximum spacing that could be allowed.

Jan 1, 1955

By Godfrey T. Vivian

Very often important discoveries are made in one industry that may be used to advantage in another, but, owing to the rarity that men step out of one industry into another, these discoveries remain unknown outside of the trade or profession in which they are made. The present paper is written solely with the object of bringing to the notice of mining and metallurgical engineers a centrifugal ore-concentrator which eventually may have a great application. Ore- Grading. Fig. 1 represents the action which takes place when solids of different dimensions are stirred up in a box and allowed to settle as minerals of the same size but of different specific gravity. This principle is applied practically in grading china-clay and in enriching tin-slimes. In the latter case the slimes are stirred around in a tub with water and allowed to settle while at the same time the side of the tub is struck with a hammer. The colloidal slimes are then poured off and various slices taken off horizontally. The great drawback of this process is that the particles are deposited horizontally and all the colloids are lost. Fig. 2 represents the action in which the particles are deposited side by side. Here the drawback is the great length of the box needed in order to prevent excessive loss. The alternative to lengthening the box is to increase the force of gravity. Centrifugal force may be regarded practically as the force of gravity augmented. Fig. 3 illustrates the Gee centrifugal machine for grading ores. The drum, A, fitted with a box, B, is mounted on a shaft or spindle, C, the whole being suspended from a ball-bearing of special design at D, supported between girders, E. Rota-

Jan 1, 1913

By Leonard Larson

BEFORE direct or wet smelting of copper concentrate was adopted at the McGill smelter, in November 1932, actual furnace smelting tests had indicated the possibility of smelting between 400 and 500 dry tons of wet concentrate per furnace day. Under calcine smelting practice, solid charge up to 1165 tons per furnace day had been smelted. It was realized that in order to smelt wet tonnage in equivalent amount per furnace day, a higher combustion rate and higher temperatures would be neces-sary within the furnace. The reverberatory furnace considered in the following history of wet-smelting de-velopments is a unit 127 ft. long and 28 ft. 8 in. wide, inside dimensions (Fig. r). This furnace was in operation through all the years from 1934 to date. During 1933, the first complete year of direct or wet smelting, the plant was on a curtailed copper-production basis and the available concentrate tonnage to be smelted was limited. The average coal-firing rate in the reverberatory for that year was 124 tons per furnace day. This rate was lower than the average for years immediately preced-ing under calcine smelting practice. With this coal-firing rate, an average of 391 tons of new metal-bearing material (N.M.B.M.) was smelted per furnace day. The following year, 1934, the coal-firing rate was in-creased to 139 tons and the smelting rate increased to 448 tons N.M.B.M. per fur-nace day. In succeeding years production required that either more tonnage be smelted in the one furnace or an additional furnace be placed in operation. With this situation confronting the smelting depart-ment, it was determined to continue the program of increasing the coal-firing rate and also to intensify the temperature in the smelting zone of the furnace. In order to accomplish this, various improvements were made to aid combustion within the furnace. The burners were enlarged, in-creased primary air was supplied to the burners, and changes were made in the furnace to enlarge and streamline the out-let, thus increasing the furnace draft.

Jan 1, 1940

By John Vanderwilt

THE value of molybdenum as a ferroalloy has been known for many years. For a long time, however, the metal was used only on a small scale in the iron industries, because the known source of supply appeared inadequate and the cost to the consumer was not stabilized. The world's production of molybdenum prior to 1914 was only a few thousand pounds per year and even during the war period annual production was only about 800,000 lb. Production during 1929 and 1930, however, was over 4,000,000 lb. per year and that of 1931 promises to be of the same order of magnitude. This remarkable increase in production is due primarily to the development of a large molybdenite deposit at Climax, Lake County, Colo., which has accounted for 80 per cent of the world's production of molybdenum during the past two years. Based on conservative esti-mates, the deposit at Climax has the capacity to maintain its 1929 and 1930 rate of production for 100 years or more. The production of molybdenum ores has been established on a new basis-in recent years as compared with the period during and before the world war. During the earlier period, production came from small deposits and the cost to the consumer fluctuated. At present, production comes from a few large deposits and the price is not only lower but also fairly constant. In recent years the price of molybdenum has consistently dropped as consumption increased. The present price is $0.95 per pound of molybdenum in ferromolybdenum and $0.80 for molybdenum in calcium molybdate. Before and during most of the war, Australia, Norway, and a few other foreign countries were the chief producers, while at present the United States is producing over 90 per cent of the world's production. With molybdenum available at a moderate cost, the steel industry has been adopting more and more the use of molybdenum as an alloy addition. A relatively small demand for molybdenum exists in the chemical and electrical industries, but the recent large increase in con-sumption has in large part been by the iron and steel industries, which

Jan 1, 1932

By R. J. Wygal, J. Naar

An equation for three-phase (water, oil, gas) imbibition oil permeability is developed, assuming the water to be the dominant wetting fluid. Oil isoperms are obtained for consolidated sandstones characterized by 1/pc2 = CS*. The evolution of an oil-gas system imbibing water from Swi to(Sw,imb )max is shown to proceed along a line of constant oil saturation with increasing oil permeability and decreasing gas saturation. When the gas satuation cannot be reduced further, the system evolves along a line of constant Sg with decreasing oil saturation and permeability. The initial gas saturation is shown to reduce markedly the effect of complete wetting by either oil or water on flow performance. INTRODUCTION Imbibition oil isoperms are required for performance prediction when a well is producing water, oil and gas. This situation occurs in multiphase displacements such as underground combustion, steam injection and the water flooding of highly depleted reservoirs. In a recent paper,1 a model was presented for the prediction of two-phase imbibition characteristics. This paper extends the imbibition model to the case of three phases by assuming that the water is the dominant wetting fluid. The following results were obtained from the model: (1) an analytical expression of oil isoperms; (2) oil isoperrns as functions of reduced water, oil and gas saturations, valid for all sandstones having a capillary pressure curve which can be approximated by 1/PC = CS*; and (3) evaluation of the three-phase flow performance as dictated by complete wetting by either oil or water. The agreement between predicted and observed oil recovery in the presence of a gas phase, reported in Ref. 1, is a partial support for the present development. However, experimental data are not available at this time to check fully the model predictions. Perhaps this paper will stimulate the collection of such data. The imbibition model of a porous medium has been described previously, and the reader is referred to the paper of Naar and Henderson1 for details. In brief, the model is formed by the random interconnection of straight capillaries, with a provision for the blocking of the non-wetting phase by the invading wetting fluid. The following expressions were derived from the model. 1. The amount of oil blocked by the invading water is

By Sullivan T. D, Lohe E. M

Geological structure is one of the main controls on ground conditions within mining. It has a significant impact on the mining conditions and productivity of coal mines within the Sydney - Bowen Basin. The three main types of faults common to this region, normal, reverse and strike-slip systems, each present distinct challenges to mining. These systems effect a wide range of geotechnical and mining conditions within the mines. These include coal quality, strata stability, goat and caving behaviour, productivity and maintenance schedules of mining equipment, mine design and mine-site stress fields. A better understanding of the regional, local and mine-scale structural setting, timing relationships of structural events and the mechanisms of fault formation will greatly aid industry's push for greater productivity and competitiveness.

Jan 1, 1991

By Tyson G. R

A novel system has been developed using computer imaging techniques to make on-line measurements of material on a moving conveyor. Meas- urements of the mass or volume of conveyor materials are important in large open pit mining operations such as those operated by the State Elec- tricity Commission of Victoria (SECV). Such on-line measurements can be used for monitoring and controlling the production and transport of coal or overburden, and to assist in maintaining production levels. This paper describes a conveyor burden volume measurement system which is currently under development at the Research and Development Department of the SECV and although targeted initially for use in the Commission's open cut mines, the system is suitable for use on any open conveyor system. A basic developmental system has been built to demon- strate the viability of the technique used and further work on the system is planned. The measurement technique and the major components which have been developed as part of the system are described, some comparisons are drawn with other existing measurement systems and potential errors and future development are discussed.

Jan 1, 1989

By C. S. Smith, Chih-Chung Wang

D. Turnbull—In the opinion of the writer the most interesting result described in this paper is that the distribution of tin with respect to solidification temperature has several fairly well-defined maxima. It appears that each peak may be associated with a catalytic impurity of some rather specific composition. Recently we have obtained some additional evidence in favor of this viewpoint in experiments on the supercooling of lead droplets coated with different surface films. The distribution of lead droplets, ostensibly coated with lead sulphate, with respect to solidification temperature exhibited two distinct and reproducible maxima, one at 20" supercooling and the other at 47". On the other hand, when the droplets were ostensibly coated with halide films, no solidification was perceptible until the aggregate was supercooled more than 55". Upon further cooling a single well-defined peak centering at 60" supercooling was observed. Since the particle size distribution was the same in these two sets of experiments it appears that the most reasonable interpretation of the results is that the sulphate surface film or its reaction products with lead are much more effective in catalyzing the nucleation of lead crystals than are lead halide films. C. S. Smith (authors' reply)—Dr. Turnbull's experiments with lead drops coated with various surface films are most interesting. However, before drawing conclusions from the cooling curves described in the paper as to the existence of a few nucleus types effective at a few different temperatures, one must consider the state of subdivision of the liquid metal. In the A1-Sn alloy used, the tin was not in uniform droplets but tended to collect in three distinct shapes—in long interconnecting prisms along grain edges, in somewhat elongated interdendritic branching pools. and in isolated droplets. A single nucleus will solidify only the metal in contact with it, and the heat evolved will be proportional to the connected volume. A uniform distribution of nuclei of random effectiveness in such an alloy will cause peaks on the specific heat curve on cooling, which correspond to the volume distribution of tin and tell nothing about the nucleus type. In any real alloy both effects will be combined, and it seems impossible at present to distinguish between them. M. B. Bever—The thesis of this interesting paper is supported by a combination of positive and negative evidence. The authors have shown that under certain conditions a liquid phase may undercool, if it is dispersed in a thoroughly discontinuous manner throughout a solid matrix. They also found that undercooling

Jan 1, 1951

By J. Parke Channing

We are accustomed to think that we are efficient in the United States, particularly with respect to such things as mining and manufacturing. The conduct of the war has demanded in England and in France a complete readjustment of manufacturing methods and plans, and today England, is probably as efficient a country as there is in the world, not even excepting Germany. This is all the more remarkable because it has been notorious for years that England has been inefficient in her manufacturing and the country has been flooded with things "Made in Germany.'' Today England is almost a socialistic community and the State is doing almost everything. England is now in such a position that practically everyone in the country is engaged in industry necessary for the conduct of the war, and this has been accomplished by increasing the efficiency both of her tools and of her man power. In the United States we certainly have been efficient so far as machines and perhaps so far as methods have been concerned, but we have not been efficient in the utilization of our man power. Before the war, our labor was undoubtedly far more efficient than that of England, but it certainly was not so highly efficient as it should have been, and the problem that confronts us today, and will all the more confront us after the war, is to make our man power efficient. England has had a taste of what you may call State Socialism, and her laboring men are not going to be content to return to the old order of things. There is one feature of the labor problem in England which has permitted her to reach this condition of state socialism with comparative rapidity; this is that practically all of her laborers are English; she has little or no foreign population. While an Englishman may be a strong union man and ready to fight his employer tooth and nail, at heart he is still a British subject, and when his country was in danger he rose to the occasion. In the United States we have such an admixture of unassimilated foreigners that the problem is more difficult, and as yet we have not been brought to that point of stress which has arrived in England. But if

Jan 1, 1919

By P. D. I. Honeyman

CHANGING trends in concentration, involving regrinding with the subsequent production of a finely divided, high-grade flotation product, presents a real problem to the modern copper smelter. In the treatment of such a material, handling difficulties are numerous and potential possible losses may be very great. In many plants, of course, preliminary roasting of the furnace charge remains an economical necessity. Under such circumstances, the operator has no alternative except to follow orthodox roaster reverberatory practice, though taking all possible precautions to avoid excessive dust losses and bad working conditions. In other plants, roasting is not only unnecessary but would be highly undesirable, and at best the charge would be merely dried before entering the reverberatory furnace. In the latter case the possibilities of raw charging loom large. The Miami plant of the International Smelting Co. handles the entire output of concentrates of the several mining companies operating in the Globe-Miami district. All of these companies produce a flotation concentrate which, at the Miami Copper Co. particularly, is all reground and is high in grade. In addition, the Inspiration Copper Co. ships a substantial tonnage of high-grade cement copper to the smelter from its leaching plant. Following the flow sheet of the original plant, all such material received was bedded, dried in Wedge furnaces and smelted in reverberatory furnaces. At times during the history of the plant it has been necessary to carry the drying operation further, to a partial roast, before reverberatory smelting. Since the charge contained over 80 per cent flotation concentrates, the handling of which in a dried condition was at best a dusty job, unusual precautions were taken to cut down dust losses. The Wedge furnace plant was equipped with a Cottrell treater and all hoppers and calcine cars were carefully designed to cut down dust loss in transferring the so-called calcine from hoppers to car and from car to furnace. In the furnace itself the dusting problem was a severe one. Arch erosion was very rapid and flues and waste-heat boilers rapidly filled up with a partly smelted flue dust.

Jan 1, 1932

Operating Characteristics of Centrifugal Fans and Use of Fan Performance Curve Discussion of paper by. Louis W. HUBER, presented at the New York Meeting, 1926, .and issued, as Pamphlet No. 1542-A, with MINING AND METALLURGY, February, 1926. G. BRIGHT, Pittsburgh, Pa.-Apparently from the pressure curves for a forward-curved-blade fan, in Mr. Huber's paper, practically all ventilation-might be stopped with increased resistance. In order, to discuss the characteristics of a fan we need, some better way to measure the characteristics of a mine. You all know that. the average anemometer is not very-reliable. Sometimes two anemometers, supposed to be recently calibrated, will differ 50 per cent. Either this or some other committee should standardize measuring methods. The characteristic curves of fans, given by Mr. Huber, would indicate that the forward-curved-blade fan would cause trouble in attempting parallel operation, because two machines will not parallel unless they have dropping pressure characteristics. On the other hand, it is indicated that with the backward-curved blade, they could easily be paralleled. But few mines use more than one fan. Mr. Huber said that if the resistance of the mine was considerably more than contemplated, the quantity of air might be such that the efficiency of the backward-curved fan would be seriously affected, dropping say from 70 to 55 or 50 per cent. In such event, could a difference of speed be selected for the fan that would give the quantity desired at a higher efficiency? L. W. HUBER, Pittsburgh, Pa.-The backward-curved-blade fan responds to change in speed the same as any other fan; if' the speed is doubled, the quantity of air is doubled, the pressure is increased four times and the horsepower eight times. One point not mentioned in the paper is that the backward-curved fan is more efficient than the forward-curved or any other type. If the latter were more efficient, it would pay to install that type and keep the resistance of the mine constant, which is hard to do but it can be done with care. But the total mechanical efficiency of a fan with backward-curved blades is from 10 to 20 per cent. higher.

Jan 1, 1927

By F. L. Bosqui

Discussion of the paper of F. L. Bosqui, presented at the San Francisco meeting, September, 1915, and printed in Bulletin No. 101, May, 1915, pp. 997 to 1033. H. A. WHITE, Springs, Transvaal (communication to the Secretary*). -It is, as the author points out in his valuable paper, a, fact, that in many plants the "trommel washings" are allowed to become eyesores, but the simpler system of pumping the entire product direct to the tube-mill circuit will avoid the extra expense of separation and small-scale treatment when one considers the relative distance of the points and the proportionately small amount of water. It is a matter of record that in stamp batteries the increase of weight has been developed concurrently with the increased use of tube mills, but independently and on its own merits. The satisfactory duty, excellent running time, and freedom from breakages in the newer mills, such as the Modder Deep, with 2,000-1b. stamps, will probably go far in removing some of the conservative prejudices mentioned by Mr. Bosqui. The success of the City Deep trial of the Nissen stamp cannot be entirely attributed to better feed distribution and discharge effects (published experiments on two-face discharge mortar boxes showed no advantages). Attention is directed to the treatment costs given by the author both before and after the increased capacity resulting from the addition of 16 Nissen stamps at Modder B. It will be observed that the only item of cost resisting the tendency to reduction caused by increased tonnage is that of milling, which has risen 1.3c. With reference to the provision for amalgamation in the new plans, it seems obvious that a great loss of head would be eliminated by passing the tube cone overflow over a separate top series of plates; three at the top and three at the bottom will effect the maximum amalgamation. This plan is followed at the Princess Estate and Gold Mining Co., Ltd., Modderfontein Deep Levels, Ltd., and Geduld Proprietary. Mines, Ltd., but elsewhere reliance is placed upon ample cone capacity and the underflow only is passed over three plates after going through the tube mill, while the overflow is passed direct to the cyanide works; both methods avoid the largely unnecessary elevation of considerable quantities of water, fine sand and slime involved in Mr. Bosqui's scheme.

Jan 1, 1916

By Reginald S. Dean

THE widespread occurrence of manganese in low grade oxide and carbonate ores not amenable to mechanical concentration has led to extensive investigations of hydrometallurgical methods for producing a pure manganese compound suitable for further treatment. Manganese carbonate is the preferable compound. This product when fully crystalline and of not too fine crystal size is easily filtrable and stable in air. It can be converted to other compounds such as the oxides by heating in air or can be reacted with acids for producing salts. A useful hydrometallurgical process must produce relatively concentrated solutions that can be purified easily, reagents must be cyclically used, and heat requirements must be small. Neither the ammonium sulphate nor sulphur dioxide leaching processes that have been tested extensively fulfill these 'requirements. Other hereto-fore proposed processes have obvious limitations and have not been tried on a large scale. The present process is based on the discovery by the writer of a new group of aqueous manganese-ammonia complex solutions highly concentrated in ammonia, which permit rapid solution of manganous oxide to concentrations of 80 to 100 g Mn per liter and from which a fully crystalline, easily filterable manganese carbonate is precipitated by the addition of carbon dioxide and partial ammonia removal. Although the process may be carried out with many ammonium salts, commercial advantages dictate the use of ammonium carbamate, which is obtained when CO2 is passed into concentrated aqueous solutions of ammonia. If the carbamate is used, the only reagents, ammonia and C02, are volatile and may therefore be recovered from solutions and residues by heating, thus eliminating washing and extensive evaporation. Impurities are controlled easily as most metal oxides are either insoluble in the lixiviant or fail to precipitate with the manganese carbonate. Others are controlled by sulphide addition. The process has been tested extensively on a small scale on a wide variety of ores; including Three Kids, Artillery Peak, Cuyuna, and Chamberlain; as repre-

Jan 1, 1952

By Carle Hayward

THIS work was first undertaken in the metallurgical laboratory of the Massachusetts Institute of Technology in 1907 by L. A. Dickinson, E. Phelps, and V. S. Rood, under the author's direction. They attempted to determine the diagram for the system Cu2S-NiS, but several inexplicable results were obtained. The following year, P. H. Mayer with Mr. Dickinson carried, on some experiments with nickel sulphide and found that the molten material slowly lost sulphur until it reached a composition corresponding to the compound Ni3S2, established by Bornemann.1 At this point the composition remained stable. The freezing points of the mixtures gradually fell off with the loss of sulphur. Since the above facts seemed to explain the erratic results obtained in the first experiments, Mr. Mayer with F. Jaeger attempted in 1910 to establish a correct equilibrium diagram for the Cu2S-Ni3S2 series. They prepared pure Cu2S and Ni3S2 and determined the cooling curves for various mixtures. The fusions were made in a platinum resistance furnace and the temperatures were measured with a platinum-iridium thermocouple connected with a Sullivan galvanometer. The curve was established for mixtures containing more than 40 per cent. Cu2S, but they were unable to determine certainly the direction of the curve beyond that point. Nothing further was attempted with this series until the present year, when the work was carried to a successful conclusion with the assistance of A. Butts, Jr., and E. H. Weil. The results of this work are given in the following pages.

Jan 1, 1914